Summary/Abstract The problem of antimicrobial misuse is well known and is a high priority action item for all of the major public health, infectious disease and US primary care societies. This reflects the existence of untreatable bacterial infections, a shallow manufacturer pipeline for new antibiotics, and continued misuse of antimicrobials by providers. In the neonatal intensive care unit (NICU) setting, antibiotics are the most frequently used medications, and very often inappropriately. Such use is associated with increased bacterial resistance, increased hospital length of stay, necrotizing enterocolitis, and even death. Drug usage decisions can be difficult in the NICU as infectious and non?infectious conditions present similarly often leading to empiric overtreatment. Thus, it is not surprising there is substantial variation in antibiotic use among NICUs. Antimicrobial stewardship programs (ASP) mitigate against the consequences of poor antibiotic use resulting in improved patient outcomes, fewer adverse events, improved bacterial susceptibilities, and economic savings. Several ASP strategies are recommended, however common implementation problems include lack of provider buy?in, consensus on best practice, attention to interactions among prescribers and other staff who manage patients, and tailoring of ASPs to clinical and institutional contexts. These challenges are exacerbated in settings in which high heterogeneity in patient indications and lack of expert consensus on treatment is present, such as the NICU. We propose to evaluate an innovative, scalable antimicrobial stewardship intervention called ECHO? ASP in NICUs participating in the largest statewide perinatal QI collaborative in the US. The intervention pairs prospective feedback (an ASP practice recommended by CDC) with the ECHO tele?learning platform (Extension for Community Healthcare Outcomes). ECHO is an evidence?based method of practice dissemination used globally in >120 health collaborations since 2003. Both parts of the ECHO?ASP intervention?prospective feedback and the ECHO methodology?are grounded in an expert?facilitated, case?based learning model tailored to how clinicians are inclined to learn and build practice consensus. The Specific Aims of the project are to: 1) Evaluate the implementation of the ECHO?ASP intervention including barriers and facilitators to implementation, site participation in video?based prospective feedback and audit sessions, dissemination of session results to other local NICU prescribers, perceived acceptability and durability of the intervention, and practice consensus on antibiotic prescribing; 2) Evaluate the effectiveness of the ECHO ASP intervention on patient care outcomes, including antibiotic use, drug?related adverse events, and other clinical complications; 3) Evaluate the cost implications of the ECHO ASP intervention, including implementation costs and effects on costs of care.